It's something that can be frustrating but you have to remember that the authors of a 3D environment has a big picture in their head and that doesn't include the glitches. We are used to see them in every 3D environments except they weren't initially planned. Human mind & behaviour has created this side activity not the opposite. There's no 3D game with the sole goal of finding glitches and exploits. It's an activity that his part of the deal but wasn't planned at all.
For Cyan, there are Easter Eggs, they did (in the past) patched some holes but they don't anymore. They don't have the time & funding anyway.
For the balcony jump, it was surely really nice back in 2003 when the bevin was not reachable in any other way. Skydivers back then were entering a new world litteraly... These days, apart from the thrill of it, there's nothing really to it. You cannot reach any secret location either. The bevin main section was closed to exploration and the seed/egg room was locked down <--- that was the secret location. Now just a simple visit to your hood age will be enough to see that these out-of-reach locations are rather normal zones.
There are more locations to explore. I'll invite you to look at some of my posts on MOULa's forum. You should have a lot of insight on what can be reached. Type "Info Central", "skydiving" and/or "Release" in search engine alongside my name, you'll find my posts. I made more than 150 marker quests to reach everything that is possible to reach.
I think we are going far off-topic right now on this thread, the main issue of it has been already solved.